Storage area networks (SANs) are typically implemented to interconnect data storage devices and data servers or hosts, using network switches to provide interconnectivity across the SAN. SANs may be complex systems with many interconnected computers, switches, and storage devices. The switches are typically configured into a switch fabric, and the hosts and storage devices connected to the switch fabric through ports of the network switches that comprise the switch fabric. Most commonly, Fibre Channel (FC) protocols are used for data communication across the switch fabric, as well as for the setup and teardown of connections to and across the fabric, although these protocols may be implemented on top of Ethernet or Internet Protocol (IP) networks.
Typically, hosts and storage devices (generically, devices) connect to switches through a link between the device and the switch, with an node port (N_port) of the device connected to one end of the link and a fabric port (F_port) of a switch connected to the other end of the link. The N_port describes the capability of the port as an associated device to participate in the fabric topology. Similarly, the F_port describes the capability of the port as an associated switch. As each device connects to the fabric, FC protocols define a fabric login mechanism to allow the N_ports and F_ports to negotiate addresses and service parameters. Further login mechanisms are defined by FC protocols to establish sessions between two N_ports and to establish sessions between processes running on devices using connected N_ports. As part of fabric login, worldwide names (WWNs) are assigned to ports and devices. In addition, each port is assigned an address, also known as a port ID, that is used in FC protocols for identifying the source and destination of a frame of data. The switches can then use the port IDs for determining the outgoing port to which an incoming frame should be sent. A name server provides a mechanism for devices to register their presence in the fabric, submitting the port ID, WWN, port type, and class of service to a database that is replicated across the fabric to name servers on all of the switches in the fabric.
Over time, SANs have become more complex, with fabrics involving multiple switches, connected with inter-switch links (ISLs). In some SANs, a core group of switches may provide backbone switching for fabric interconnectivity, with few or no devices directly connected to the core switches, while a number of edge switches provide connection points for the devices or devices of the SAN. Additional layers of switches may also exist between the edge switches and the core switches.
These edge switches may not need the full capability of the core switches, but conventional switches have often been unable to offer reduced capability, so that edge switches have been used that are more complex than would be desirable. Thus, the cost of edge switches has been greater then desired, and the SAN resources expended for managing such switches may be more than would be necessary if reduced-capability switches were available.
In addition, virtualization has affected the manageability of SANs. Virtual devices may from time to time migrate from one physical device to another physical device or from one N_port to another N_port in a multiply connected physical device. Thus, fabric services such as name services have required more resources to handle the migration than would be desirable.